There has recently been a convergence of functionality as between cellular telephones, personal digital assistants (PDAs), and still and motion video cameras. The convergent devices give rise to several types of data services with different quality-of-service requirements associated with computer network transmission. For example, motion video and corresponding audio streams, while able to tolerate packet loss without replacement during transmission, are severely affected by long data transmission delays. Financial data streams (e.g., online banking, online bill paying and online purchases) are tolerant to packet loss (with replacement) during transmission, but are not sensitive to transmission delays. Finally, data streams such as electronic mail messages and web services are tolerant to both packet loss (with replacement) and long delays.
Convergent devices thus need to be able to simultaneously handle these different types of services.